Knitting machines often employ a plurality of knitting needles that are moved reciprocally in concert with one another to form a knitted fabric. Often, the knitting needles are reciprocated by a cam which defines an undulating track which urges the knitting needle to and fro. For example, many circular knitting machines have a cam which defines a recessed slot, or track. The needles used with such slotted cams have a longitudinal shaft from which a protrusion known as the butt of the needle extends. This butt of the knitting needle is received within the recessed cam track. The cam track generally defines an undulating path which the needle butt must follow as the butt is moved relative to the cam in a direction transverse to the longitudinal axis of the needle. Thus, the undulating sides of the cam track engage the needle butt and cause the knitting needle to move in a reciprocating fashion.
To increase efficiency and productivity, it is often desirable to maximize the speed at which the knitting machine may be operated. However, it has been found that increasing the operating speed of the knitting machine can impose severe stresses and increased wear on the knitting needles. As machine speed increases, the speed of reciprocation of the knitting needles installed in the machine likewise increases, and the cycle time for a complete reciprocation of each needle decreases.
As a result of the increasing machine speed, the initial force which is generated when the needle butt impacts the edge of the cam track is also greater than in machines operating at slower speeds. This impact and the forces associated with sliding of the needle butt within the cam track may cause increased wear of the needle butt. The impact may also cause the needle to vibrate. These vibrations may be transmitted from the butt to the shaft of the needle, and further, along the shaft of the needle to the hook at the end of the needle. Because the hook of the needle is relatively weak, it has been found that this increased impact causes greater breakage and wear of the needle hook.
Prior attempts to reduce needle wear and breakage have included modification of the cam track itself. Since the momentum of the needle increases as it is reciprocated at higher speeds, closed cams have been developed having wave-like needle guiding grooves. However, these closed cams have a fixed groove size. Also, modern cams have tracks which have angles of inclination that vary from point to point. Because of these variations, it has been found that the edges of the needle butt may not contact the edges of the cam track smoothly, which is another source of vibration and wear of the needle. In the past, this problem has been partially ameliorated by beveling the corners of the needle butt. However, this measure has not met with the desired success because the relatively small beveled surfaces at the corners of the butt do not provide a large contact area and generally do not conform to the inclination angle of the cam track. As a result, significant butt wear and vibration may still result when the butt impacts the cam track. Additionally, the beveled corners do not permit smooth sliding of the needle butt along the cam track.
It is sometimes desirable to use needles of different gauges in a machine. For example, a 28 gauge needle may have a thickness of about 0.42 mm, whereas an 18 gauge needle may be about 0.65 mm thick. Thus, the difference in thickness between a 28 gauge and an 18 gauge needle is 0.23 mm. If the same cam is used with an 18 gauge or 18 gauge needle, the clearance between the needle butt and cam track may vary according to the thickness of the needle. In the foregoing example, the clearance variation could be as about 0.23 mm if the inclination angle of the cam were about 45.degree..
It is necessary to insure that the clearance between the cam track and butt is appropriate in order to minimize breakage and wear of the knitting needle due to impact. If the clearance between the cam track and butt is too great, the frequency of needle breakage and the amount of wear of the needle butt are increased. However, if the clearance between the cam track and butt is too small, breakage of the needle butt may result.
Since the clearance between the needle butt and the cam track varies with the needle gauge, it has heretofore sometimes been desirable to change the cam when the gauge of the needles in the machine is changed to insure that the clearance between the needle butt and cam track sidewalls remains appropriate. However, changing the cam is quite expensive. As a result, it is desirable to be able to change the gauge of the knitting needles used in the machine without changing the cam in the machine without encountering the problems associated with improper butt--cam clearance.
In light of the aforementioned deficiencies, it is an object of the present invention to provide a new knitting needle having a butt which permits different gauge needles to be used on a machine having a single size cam track.
Another object of the present invention is to provide a knitting needle for use in knitting machines which has a butt that facilitate smooth sliding of the butt along the sides of the cam track.
Yet another object of the present invention is to provide a knitting needle for use in knitting machines having a butt which mitigates the impact forces between the cam track and needle.
A still further object of the present invention is to provide a knitting needle having a butt which experiences less wear when used in a knitting machine.
A further object of the present invention is to provide a knitting needle having a butt which reduces the wear and breakage of the needle hook associated with use.
Another object of the present invention is to provide a knitting needle having a butt with faces that engage the cam track so as to reduce the amount of vibration within the knitting needle.